Influences of growth temperature on the crystalline characteristics and optical properties for ZnO films deposited by reactive magnetron sputtering

Abstract

Using reactive radio-frequency magnetron sputtering, ZnO films with strong c-axi s orientation have been deposited on Si (100) substrates at temperatures ranging from room temperature (RT) to 750℃. We have studied the influence of growth te mperature on the structural characteristics of the as-deposited films in morphol ogy, grain size, microstructure, and residual stress by using atomic force micro scopy, transmission electron microscopy, X-ray diffraction, and Raman spectrosco py. With the measurement of the transmission spectra and photoluminescence (PL) properties, the relationship between the crystallinity and optical properties of ZnO films have been discussed. It is found that the grain size increases with t emperature up to 500℃, and then decreases at 750℃. ZnO grains have an epitaxia l relationship with Si (100) substrate for the films deposited at the temperatur es ranging from RT to 750℃. The films deposited below 500℃ are in the states o f compressive strain while the film deposited at 750℃ is in tensile. The differ ence in growth temperature results in the variation of refractive index, extinct ion coefficient, optical energy gap, and PL properties of the films. It is concl uded that growth temperature dominates the PL behavior of ZnO films. We also dis cuss the physical mechanism affecting the PL behavior.